Although gravel and coarse sand make up significant portions of some environmentally important sediments, hydraulic properties are typically obtained in the laboratory using the < 2 mm size fraction. Published reports suggest that gravel content can significantly affect hydraulic properties of the bulk soils. However, commonly used gravel correction methods are not always applicable over the range of conditions observed at DOE waste sites. In this study, we use the power-averaging method, with the power being a function of gravel content, to quantify the effect of grain size and to predict the saturated hydraulic conductivity, Ks, of a binary mixture comprised of fine and coarse fractions. Mixtures of 20/30 accusand (0.59 mm < d < 0.84 mm) and glass beads (d =5 mm) were prepared and Ks measured as the sand content increased from 0 to 100 percent. Results show that there exists a critical coarse fraction, fc at which porosity and Ks reaches a minimum. For a gravel content < fc, the bulk Ks decreases with increasing gravel content due primarily to a decrease in porosity. For gravel content > fc, the bulk Ks increases sharply as gravel content increases. These results are used to develop a generalized gravel correction approach that shows good agreement between measured and predicted Ks over the full range of gravel content. The Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle under Contract DE-AC06-76RL01830.